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題名 | 坡地水流動力分析之研究=Dynamic Analysis of Flow on a Slope |
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作者 | 陳右錚; 褚思穎; 謝平城; | 書刊名 | 水土保持學報 |
卷期 | 41:1 2009.03[民98.03] |
頁次 | 頁45-62 |
分類號 | 434.278 |
關鍵詞 | 漫地流; 孔隙介質流; 層流; Overland flow; Porous media flow; Laminar flow; |
語文 | 中文(Chinese) |
中文摘要 | 本研究以水動力學的觀點,探討坡地水流之水理現象,包括裸露地及具植生覆蓋但水深不 及草高等兩種地表條件下之流況分析。將流場分成均質水層及可透水土層或植生層及可透水土 層二個區域,以層流模式建立完善的理論依據並推求水流流經地表時之速度解析,希望藉此瞭 解植生存在對水流流速的影響。文中除了將底床之土壤視為具滲透性之多孔介質,考慮其透水 地表之流速不為零的真實現象外,亦將植生層視為一多孔介質,而植被內與土壤中流動的水流 則以孔隙介質流視之。 在層流流況中,以簡化之那維爾-史托克斯方程式(Navier-Stokes equation)搭配宋長虹(1993) 根據Biot 多孔彈性介質理論所建立之多孔介質層流模式為控制方程式,對整體流速分佈進行求 解。發現流速會隨水深、坡度變大而增加,草層植生愈稀疏、土層之滲透性愈佳,亦會使流速 增大,但土層之滲透性對地表以上之流速無甚大之影響。 於獲得解析解之後,估算漫地流流經草地或裸露地之平均流速,並與Darcy-Weisbach 公式 及運動波方程式相互比較,運動波方程式計算得平均流速為最大,本研究之裸露地計算結果介 於運動波方程式及D-W 公式計算得平均流速之間。當草層植生愈稠密,本研究水深不及草高 之計算結果與D-W 公式計算得平均流速相交於水深愈低時;而草層植生稀疏至n2 > 0.94 且水 深在0.05 公尺以下時,D-W 公式之計算結果則為最小。 |
英文摘要 | Hydrodynamics will be applied to delineate the overland flow in this study. This investigation includes the cases of flow passing over a bare ground and vegetative ground. In this study, we aim to figure out how vegetation influences streamwise velocity by analyzing the velocity of flow passing vegetative ground and dividing the flow field into two regions: homogenous water-layer/ vegetation-layer and permeable soil-layer. The soil and vegetation are both regarded as porous media and the flow inside the two layers is porous media flow. Thus the nonzero velocity at the ground surface could be estimated. The velocity distribution in laminar flow is solved by simplified Navier-Stokes equations and Song's (1993) laminar model based on Biot's poroelastic theory. In addition to the development of the fundamental theory, the analytical solution of the velocity profile will be obtained. The velocity will increase when the water depth, the slope or the porosity of vegetation-layer increase. The better permeability of soil layer will increase the velocity, but it has little influence on the velocity above the ground. After the analytical solution of the velocity profile is obtained, the average velocity of overland flow passing over a vegetative or non-vegetative sloping plane is also calculated. The average velocity of this study is compared with those calculated by Darcy-Weisbach definition and kinematic-wave equation, respectively. The result of kinematic-wave equation is the largest. When the flow passes over a bare ground, the present result is between the result of kinematic-wave equation and that of D-W definition. When the vegetation becomes denser, the average velocity of the vegetative ground and that of D-W definition cross at lower depth. When n2 > 0.94 and h < 0.05m, the result of D-W definition is the smallest. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。